This invention relates to a process for preparing compounds corresponding to the formula (I) CF.sub.3 CCl.sub.2 X, wherein X=Cl or H, by rearrangement using an AlCl.sub.3 catalyst.
CF.sub.3 CCl.sub.3 is a starting material for chemical synthesis. For example, it can be reacted with SO.sub.3 to give trifluoroacetyl chloride, which in turn is used in chemical synthesis. By hydrogenating CF.sub.3 CCl.sub.3 (R113a), chlorofluorohydrocarbons can be prepared which are used as substitutes for fully halogenated carbon compounds, as solvents or propellants. CF.sub.3 CHCl.sub.2 is such a solvent or propellant. It is already known that, for example, CF.sub.3 CCl.sub.3 can be prepared by rearrangement of CF.sub.2 ClCFCl.sub.2 over aluminum chloride. A drawback of this reaction is that it starts up only at elevated temperature, but then takes place with large amounts of heat being released, so that the batch is often observed to run away.